Add __str__ to models, remove null=True in CharField and TextField

apps/note/models/notes.py

@@ -70,8 +70,8 @@ class Note(PolymorphicModel):
                          "It can be reactivated at any time.")),
             ('forced', _("The note is blocked by the the BDE and can't be manually reactivated.")),
         ],
-        null=True,
-        default=None,
+        blank=True,
+        default="",
     )
 
     class Meta:

apps/note/models/transactions.py

@@ -90,6 +90,9 @@ class TransactionTemplate(models.Model):
     def get_absolute_url(self):
         return reverse('note:template_update', args=(self.pk,))
 
+    def __str__(self):
+        return self.name
+
 
 class Transaction(PolymorphicModel):
     """
@@ -150,8 +153,7 @@ class Transaction(PolymorphicModel):
     invalidity_reason = models.CharField(
         verbose_name=_('invalidity reason'),
         max_length=255,
-        default=None,
-        null=True,
+        default='',
         blank=True,
     )
 
@@ -195,7 +197,7 @@ class Transaction(PolymorphicModel):
 
             # When a transaction is declared valid, we ensure that the invalidity reason is null, if it was
             # previously invalid
-            self.invalidity_reason = None
+            self.invalidity_reason = ""
 
         if source_balance > 9223372036854775807 or source_balance < -9223372036854775808\
                 or dest_balance > 9223372036854775807 or dest_balance < -9223372036854775808: